The mechanism(s) of action of the anticarcinogenic proteinase inhibitors is of interest because they have been shown to suppress tumorigenesis both in vitro and in vivo. Their mechanism of action may, in part, involve effecting plasma membrane proteinases. Our broad, long term objectives are to study the role of proteinases in the regulation of normal cell function and, in turn the mechanism of cell transformation. This specific project will isolate and characterize specific plasma membrane proteinases, evaluate their importance in the mechanism of in vitro cell transformation, identify their normal cellular function/substrates and in turn identify a mechanism of anticarcinogenic action for proteinase inhibitors. Specifically, we plan: 1. To isolate and characterize a plasma membrane proteinase which is inhibited by anticarcinogenic proteinase inhibitors; 2. To prepare polyclonal and monoclonal antibodies to the plasma membrane proteinase as tools for studying cellular localization and function 3. To identify the 'receptor' for proteinase inhibitors using photoaffinity-labelled proteinase inhibitors and HPLC characterization 4. To evaluate, with respect to proteinase inhibitors and antibodies, the cellular mechanism of transformation suppression 5. To identify cellular substrates involved in a model for the anticarcinogenic mechanism of action of proteinase inhibitors.